1. Field of the Invention
The present invention relates to an anti-skid braking control system for preventing wheel lockup during abrupt braking to achieve stable braking, improve steering control, and reduce stopping distances, and more particularly to an anti-skid braking control system of a simple construction which is capable of controlling a plurality of wheel brake cylinder pressures independently of each other.
2. Description of the Prior Art
Japanese Patent Publication No. 58-50903 discloses an anti-skid braking system for use on a motorcycle. The disclosed anti-skid braking system is structurally simpler than a four-wheel anti-skid braking system in that it has no reservoir.
If the conventional anti-skid braking system which has no reservoir is incorporated in a four-wheel automobile, then various problems will be caused as described below. In order to control four wheel brake cylinder pressures independently of each other, a total of four fluid pressure pumps each for one wheel brake cylinder are required, but their combined size is large. The entire pump assembly can be reduced in size by controlling two wheel brake cylinders with braking fluid pressures supplied from a single common fluid pressure pump. However, in the event that there is a difference between the two wheel brake cylinder pressures, another problem tends to arise. More specifically, when the braking fluid pressures in two wheel brake cylinders differ from each other, only the higher braking pressure is reduced by the pump, but the lower braking pressure is not lowered since no braking fluid flows from the wheel brake cylinder containing the lower braking pressure into the inlet port of the pump. Stated otherwise, if the braking pressures in the two wheel brake cylinders are reduced by the common pump, there is an instance in which the braking pressures for the two wheels may not be independently controlled.